The invention concerns a device for supply of heat to body tissues according to the preamble of Patent claim 1.
With certain kinds of conditions caused by diseases involving unnatural growths in tissues, treatment with heat gives a good result after treatment. The tissue is heated to the degree that it dies. Examples of disease conditions of this kind are certain types of cancer and benign prostate hyperplasia, BPH. With treatment certain parts of the tissue are heated so that death of the tissue occurs, while other parts of the tissue must or should be protected. The conditions of disease which are primarily focused on here are those which occur in tissue surrounding cavities in the body. As examples beyond that mentioned above cancer of the esophagus, trachea, urethra, and intestine can also be mentioned.
Corresponding conditions of disease can also occur in animals, where similar treatment can be applied. Above all, treatment of domestic animals such as, for example, dogs can become topical.
In order to produce heat, different devices can be employed. Laser, microwave, and radio frequency antennas are usually used. A method using the insertion of a container with liquid into the bodily cavity is also known. The liquid expands the container so that good contact against the surrounding tissue is achieved. The liquid is then heated either by supplying warm liquid through a circulating system or by supplying energy to a heating device within the container from which heat is transferred in some way to the liquid and then to the tissue.
Since the volume of the tissue which will be treated varies as well as the ability to absorb heat in this tissue and adjacent tissue, which will not be treated, it is appropriate that continuous monitoring occur during treatment. When treatment is in progress, the heating of tissue occurs. The heating should occur within certain temperature ranges for the best result of the treatment. At too high a temperature unnecessarily great damage occurs in the tissue and at too low a temperature the desired result of treatment does not occur.
It is common that the device for heating incorporates some form of temperature sensor that is arrayed on the element inducing heating in order to monitor the temperature in adjacent tissue. A disadvantage of this design is that the temperature sensor gives information more on the temperature of the element than on the temperature of the tissue.
An example of this type of heating device is shown and described in EP 0 370 890. The device encompasses a catheter contained in a microwave antenna that is embodied to emit radio energy to the tissue surrounding the antenna. The catheter is also provided with a cooling channel for cooling the tissue that is located closest to the catheter. In the catheter a temperature transducer is located for reading the temperature of the catheter. The detected temperature is thus not in agreement with the temperature of the tissue that is being treated.
A more developed method of temperature detection is shown and described in PCT/SE96/00649. In order to be able to register the rise of temperature directly in the tissue to be treated, a first temperature detection instrument according to PCT/SE96/00649 is connected with a first carrier. The carrier is led through a channel in the catheter and is devised to be extendable through an opening in the catheter. In the opening of the catheter a control device for the carrier is appropriately arrayed so that the carrier is directed into the tissue at the desired angle in relation to the catheter. The treatment carried out with the above-mentioned microwave device is often called TUMT (TransUrethral Microwave Thermotherapy).
Either the carrier or the temperature detection instrument is equipped with a tip that facilitates penetration into the tissue. The temperature detection instrument can be conventionally embodied as a resistive transducer or a semiconductor. The cabling required for transducers of this type is done via channels in the catheter. If a transducer of the optical type is used, a fiber-optic guide is provided through a channel in the catheter.
According to the devices described above and according to other known techniques, the attending physician normally determines the duration and temperature of treatment. In spite of the possibility to conduct continuous temperature detection, there are problems in securing satisfactory results of treatment during the process of treatment, since the process of healing can take up to several weeks or months. It is also difficult to adjust a treatment in process to new conditions, for example, pain arising in the patient, and to judge how the treatment in general should be adjusted to current physical conditions in the patient.
An object of the invention is to produce a device for supply of heat to body tissue, whereby the disadvantages mentioned above are essentially eliminated. This object is achieved according to the invention by the features indicated in the Patent claims 1 through 10.
According to the invention there is also the possibility of adjusting the supply of heat beforehand in different ways and to predict the result better. A device according to the invention is used in order to calculate the temperature distribution in the whole prostate based on information on it at certain points measured intra-prostatically and information on the distribution of the energy absorption in body tissue from an energy or heat source. The temperature distribution is determined on the basis of the relation between the temperature in the tissue and absorbed energy, blood flow, and heat conduction. Through continuous measurement of the temperature and the time during which heat is applied, and with continuous monitoring of the temperature distribution in relation to information on the survival of cells undergoing thermal exposure, the amount of tissue destroyed at certain points in time during the exposure is determined.
In a preferred embodiment the temperature distribution and destruction of tissue is continuously presented as image and text on a display, so that the attending physician can constantly be informed on current conditions. Heat is supplied to the tissue until a portion of the tissue that can be adjusted for has been destroyed.
Further advantages and special features of the invention can be seen by the following description, drawings, and dependent patent claims.